PDF(Pubmed)
Abstract：
The envelope glycoprotein (Env) of retroviruses, such as the Feline leukemia virus (FeLV), is the main target of neutralizing humoral response, and therefore, a promising vaccine candidate, despite its reported poor immunogenicity. The incorporation of mutations that stabilize analogous proteins from other viruses in their prefusion conformation (e.g., HIV Env, SARS-CoV-2 S, or RSV F glycoproteins) has improved their capability to induce neutralizing protective immune responses. Therefore, we have stabilized the FeLV Env protein following a strategy based on the incorporation of a disulfide bond and an Ile/Pro mutation (SOSIP) previously used to generate soluble HIV Env trimers. We have characterized this SOSIP-FeLV Env in its soluble form and as a transmembrane protein present at high density on the surface of FeLV Gag-based VLPs. Furthermore, we have tested its immunogenicity in DNA-immunization assays in C57BL/6 mice. Low anti-FeLV Env responses were detected in SOSIP-FeLV soluble protein-immunized animals; however, unexpectedly no responses were detected in the animals immunized with SOSIP-FeLV Gag-based VLPs. In contrast, high humoral response against FeLV Gag was observed in the animals immunized with control Gag VLPs lacking SOSIP-FeLV Env, while this response was significantly impaired when the VLPs incorporated SOSIP-FeLV Env. Our data suggest that FeLV Env can be stabilized as a soluble protein and can be expressed in high-density VLPs. However, when formulated as a DNA vaccine, SOSIP-FeLV Env remains poorly immunogenic, a limitation that must be overcome to develop an effective FeLV vaccine.
摘要：
逆转录病毒的包膜糖蛋白（Env），例如猫白血病病毒（FeLV），是中和体液反应的主要目标，因此,一个有前途的候选疫苗，尽管据报道其免疫原性差。在融合前构象中掺入稳定来自其他病毒的类似蛋白的突变（例如，艾滋病毒感染，SARS-CoV-2S,或RSVF糖蛋白）提高了它们诱导中和保护性免疫应答的能力。因此,我们已经稳定了FeLVEnv蛋白，该策略基于先前用于生成可溶性HIVEnv三聚体的二硫键和Ile/Pro突变（SOSIP）的掺入。我们已经将这种SOSIP-FeLVEnv表征为其可溶形式，并作为高密度存在于基于FeLVGag的VLP表面上的跨膜蛋白。此外，我们已经在C57BL/6小鼠的DNA免疫试验中测试了其免疫原性。在SOSIP-FeLV可溶性蛋白免疫的动物中检测到低的抗FeLVEnv应答;然而,在用基于SOSIP-FeLVGag的VLP免疫的动物中意外地没有检测到应答。相比之下,在用缺乏SOSIP-FeLVEnv的对照GagVLP免疫的动物中观察到针对FeLVGag的高体液应答，而当VLP掺入SOSIP-FeLVEnv时，这种反应明显受损。我们的数据表明，FeLVEnv可以稳定为可溶性蛋白，并且可以在高密度VLP中表达。然而,当配制成DNA疫苗时，SOSIP-FeLVEnv仍然缺乏免疫原性，开发有效的FeLV疫苗必须克服的限制。
